Raymond dtjbois



R. DUBOIS Sept. 24, 1929.

ELECTRIC ARC LAMP CATHODE WITH ROTARY FLAME AND STATIONARY CRATE FiledMay 14, 1925 Patented Sept. 24, 1929 UNITED STATES RAYMOND DUBOIS, OFTOULON, FRANCE ELECTRIG-ARG-LAMP CATHODE WITH ROTARY FLAME ANDSTATIONARY oRATER Application filed May 14, 1925, Serial No.

Are lamps constituted by a combustible conductive anode from which anarc is struck ending in an incombustible cathode, generally of metal andin the shape of a ring, arealready known.

The regularity of such arcs in the case of a current of above amperesmay be obtained by imparting a quick rotary motion to the flame whichthen turns around the anodical 1O crater. The anode may be constitutedby an appropriate carbon and it is cut so as to form a cavity having aregular shape. The rotary motion preferably produced by the actlon of amagnetic field is only possible where no 1m- 15 perative cause exists torender the arc stationary at a particular point of the cathode, thisalways taking place when a point of the region where the arc may beproduced reaches a temperature such that the thermlomc emlssion is moreabundant there than at the neighbouring points. The are then remainsstationary at this point; on the other hand, 1t belng nesessary tothoroughly cool; the cathode 1n order to prevent it from melting, thiscooling must be effected. By currents of amperes for instance, coolingby means of running water produced without any special care allows ofobtaining a continuous and rapid rotary motion. Things are different inthe case of higher current values or when cooling by means of air. Theproper rotation of the flame cannot be produced from 20 amperes upwardswith a cathode cooled only by air passing through it. The flame followsa c1rcumferential path even with a discharge of large quantities of airunder pressure, the flame remains stationary at a point which is rapidlyconsumed and cannot be avoided.

This invention relates to a new type of cathode which requires for itscooling the minimum quantity of a fluid, liquid or gas such as air atany desired pressure.

The cathodes constructed according to my invention are distinguishedessentially in that 4.5 the inner circulation of the cooling medium isproduced so as to maintain the same temperature whatever the considereddiametrical plane may be, in other words, every position that the flameis capable of occupying ends at a point of the cathode where thetemperature 30,205, and in France February 27, 1925.

is the same whatever the considered radius may be. Accordingly thecathode must first of all have the shape of a figure of revolution butthis condition which generally obtains in the existing cathodes is notsu'lficient; in fact the circulation of the fluid must also have thissame axial symmetry, that is to say in the region to be cooled, thecirculation of the fluid must be such that the isothermal curves are allof them circumferences centered upon the axis of the cathode. In orderto fulfill this requirement, the stream lines of the fluid in the regionto be cooled must be all geometrically identical to each other andsusceptible ofbelng represented by the postions taken successively bythe same line caused to revolve about the symmetrical axis of thecathode.

The appended drawing shows by Way of example, several embodiments of theprinciples above cited.

Fig. 1 is a sectional view through the middle part of a cathode withsymmetrical cooling around the axis.

Fig. 2 is a similar View of a cathode of the standard type withcircumferential circulation.

Fig. 3 is a sectional axial view for the same cathode as in Fig. 2.

Figs. 4, 5, 6 and 7 are sectional views showing other cathodes based onthe same principle as that of Fig. 1.

Fig. 8 is perspective view of a portion of Fig. 7.

Fig. 9 is a perspective view of the type Figs. 5 and 6.

In the mode of execution shown in Fig. 1, the cathode is constituted bya piece of copper '1 turned in a lathe, hollowed out and provided at thecentre with an edge 2 around which rotates the arc 6 struck from thepositive crater 7. The thickness of the metal in the middle partdetermines the temperature to which the point where the flame strikesout is brought, it mustbe determined according to the conditions ofworking of the arc, and is of about 2 millimeters for 25 amperes. Apartition wall formed by a disc placed at right angles to the axis ofthe cathode divides the recess 4- hollowed out in the part 1 in twocollectors or channels, 8 and9 respectively for the admission and thedischarge of the fluid. The cooling is ensured by the passage of thefluid, in the direction indicated by the arrows 4:, in the shape of auniform sheet through the region 5 directly in contact with the region 2where the heat is supplied. It is notnecessary that the supply maincarrying the fluid to the inlet collector and the dis charge main forthe other collector should have the shape of a figure of revolution ifthe section of the passages 8 and 9 is large enough to cause the flow ofthe fluid to slow down relatively to its rate of flowing in the regionof passage 5 where the section must be much smaller. In this manner thesymmetry of the stream lines is not practically altered in the importantregion even in case of the fluid being admitted and discharged throughthe same tubes, in the arrangement shown in Fig. 7.

It is to be noted that a cathode of this type differs essentially fromcathodes simply hollowed out such as the one shown in diametricalsection in Fig. 2 and in transverse section in Fig. 3. In this cathodewhich is cooled by means of a circumferential circulation, a pointlocated near the inlet, P for instance, is systematically at a lowertemperature than a point located near the outlet, such as Q forinstance. Even when the cooling fluid used is water, the difference maybe over 100, as it suffices that the arc should slow down systematicallyin the region of the highest ten'iperature to bring it to a degree ofheat such that the water will be vaporized at that point. Calefactionthen allows this re gion to become overheated. hen the cool ing iseffected by means of a gas, the diffe ence of temperature between thepoints P and Q easily reaches 200 degrees. Contrary to that whichobtains in the kind of cathodes already known of which the inconveniencehas been shown, the hot middle region receives only cold fluid or atleast fluid having a uniform temperature while in the cathodes of thetype shown in Fig. 1, that is where the circulation is radial, noadvantage is given to any direction and consequently the flame has notendency to remain stationary at any point in preference to another.

Fig. 1 of the annexed drawing is merely an example of possibleembodiments of my invention.

Fig. t shows another embodiment which may be constructed without anydifficulty and is specially advantageous even in the case of coolingeffected by air. In this last figure the same numerals designate thesame parts as in Fig. 1.

In this mode of execution the partition wall 3 is no longer separatedfrom the part 1, it is made integral with it and its middle part 5 isperforated with a great number of iden tical holes 10 in lieu of theannular passage 5, Fig. 1. The distances between the holes are reducedto a minimum consistent with the resistance of the wall or partition.

In some cases, the section of the collectors may be too small relativelyto that of the holes, nevertheless the same discharge may be obtained inall the holes by recurring to the following contrivance. The partitionwall is put out of shape by distortion as will be seen in 5 in such amanner that the section of the collectors varies progressively, the onehaving a smaller section when the other has a larger one. This largesection is then placed in front of theadmission to the discharge tube,the fluid inlet tube being placed in front of the greater section of theother collector upon the same diameter. This arrangement is shown inFig. 7. In this manner all the trajectories of the fluid through thedifferent holes are equal as regards their length and the resistanceoffered to the passage of the fluid. The size of the. holes must remainsmall. enough for the principal loss of charge to take place during thepassage therethrough, the loss in the collectors being much smaller. Thenormal working is thus the same in all the holes notwithstanding thespeed acquired by the fluid flowing in the inlet collector this speedtending to favour the nearest holes.

(lertain modifications as indicated hereafter may be made in theconstruction in order to improve the type of cathode above described.

1. The outline of the middle section is such that the luminous field islargely open, to this effect the angle of the cone directed towards thefront is very large it may be at least of 11.0 degrees.

2. The back part in the direction of the. crater is plane andperpendicular to the axis, or conical and having an angular opening ormore than 120 in order to prevent the are from getting away from theinterior edge 2 of the cathode. In fact the flame always tends to takethe position which gives it the minimum length and this outline causesthe length of the arc to increase very rapidly when it leaves the middleedge.

3. The width of the edge 2 upon which the arc revolves increases withthe strength of the lamp current because it determines the temperaturereached by the points where the arc is struck: for 10 amperes forinstance, the edge must be sharp and for 25 amperes it must be formed bya truncated bevel having a width of about 1 mm. calculated parallelly tothe axis.

41. It is advantageous to be able to replace without any difliculty theregion in which-- the are revolves and which is susceptible of wearingout slowly. To this effect the oathode may be made removable. I Fig. 7shows a diametrical section of a removable cathode. A stationary partcomprises the cylindrical bearing 11 and its pipings 12 find 13. The

removable element may be constituted b the element shown in Figs. 5 and6. The ront part and the partition wall 3 may also be made stationary,the only removable element being then the back part 15 comprising theedge 2. The division can be made at 14: by giving to the elements aconical outline which allows of obtaining a tight joint. Plastic jointsnot represented ensure the tightness of the connection with the bearing11.

In case of the edge 2 being Worn out it may be repaired by metal castingor by autogenous welding when the metal used for its construction iscopper, this metal being very suitable for the purpose.

5. The durability of the cathodes can be considerably increased bycutting out the edge 2 in a ring of precious metal unoxydable and lessfusible than copper, such as pure platinum for instance. The connectionof the precious metal with that of the cathode must be very close inorder to preserve the heat conductivity. It may be produced for instanceby setting the ring in its recess under a very high pressure or by meansof a good heat conducting brazing, such as silver brazing.

It is to be understood that any and all changes in the shape, details,substance and size of the described cathodes within the scope of theclaims hereunto appended may be resorted to without departing from theprinciple of my invention.

1 claim- 1. A stationary, hollow, ring-shaped cathode for rotary flamearcs having a partition therein perpendicular to the axis of symmetry ofthe cathode and separating the interior of the cathode into twocommunicating chambers, an entrance orifice in one of said chambers anda discharge orifice in the other chamber, said partition being locallydistorted at the entrance and discharge orifices.

2. A stationary, hollow, annular, conical cathode for rotary flame arcshaving a partition dividing the interior of the cathode into twocommunicating chambers, said chambers communicating adjacent the centraledge of the cathode, cooling fluid supply means for one chamber andfluid discharge means for the other chamber.

3. A stationary, hollow, annular cathode for rotary flame arcs, havingan upper and a lower re-entrant conical surface, a partition dividingthe space between the surfaces into two chambers and having perforationsconnecting the two chambers adjacent the narrowest space between thetwosurfaces, means to supply one chamber with cooling fluid and means todischarge said fluid from the other chamber.

4. A cathode for an electric arc with rotary flame and stationary craterwhich comprises: a hollow ring-shaped cathode, a separating wallperpendicular to the axis of symmetry designed to divide the inner spaceof the cathode in two collectors; communication openings formed in saidwall near the middle part of the cathode to be cooled; an inlet orificefor the cooling fluid opening in one of the collectors and an outletorifice opening in the other collector.

5. A cathode for an electric arc with rotary flame and stationary craterwhich comprises a hollow ring-shaped cathode the section of which isconstricted towards the middle so as to provide a large opening towardsthe front and a plane region in the direction of the crater in order tolocalize the arc towards the middle, a partition wall dividing theinterior of the cathode in two collectors, an inlet opening for thecooling fluid provided in one of said collectors, an outlet opening inthe other collector and means to cause the cooling fluid to pass fromone collector to the other in contact with the part of the cathode to becooled.

In testimony that I claim the foregoing as my invention, I have signedmy name.

RAYMOND DUBOIS.

